diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index 2aba2dfe91..1f968f0bf7 100644
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -1003,6 +1003,11 @@ mdimmedsync(SMgrRelation reln, ForkNumber forknum)
 	}
 }
 
+
+/* TEMPORARY INSTRUMENTATION */
+static int remember_req_cnt = 0;
+
+
 /*
  *	mdsync() -- Sync previous writes to stable storage.
  */
@@ -1024,6 +1029,17 @@ mdsync(void)
 	uint64		longest = 0;
 	uint64		total_elapsed = 0;
 
+
+	/*
+	 * TEMPORARY INSTRUMENTATION
+	 */
+	instr_time	mdsync_start,
+				mdsync_end,
+				mdsync_diff;
+	remember_req_cnt = 0;
+	INSTR_TIME_SET_CURRENT(mdsync_start);
+
+
 	/*
 	 * This is only called during checkpoints, and checkpoints should only
 	 * occur in processes that have created a pendingOpsTable.
@@ -1295,6 +1311,18 @@ mdsync(void)
 
 	/* Flag successful completion of mdsync */
 	mdsync_in_progress = false;
+
+
+	/*
+	 * TEMPORARY INSTRUMENTATION
+	 */
+	INSTR_TIME_SET_CURRENT(mdsync_end);
+	mdsync_diff = mdsync_end;
+	INSTR_TIME_SUBTRACT(mdsync_diff, mdsync_start);
+	elapsed = INSTR_TIME_GET_MICROSEC(mdsync_diff);
+	if (log_checkpoints)
+		elog(LOG, "debug mdsync stats: remembered=%d fsynced=%d time=%.3f msec",
+			 remember_req_cnt, processed, (double) elapsed / 1000);
 }
 
 /*
@@ -1482,6 +1510,9 @@ register_unlink(RelFileNodeBackend rnode)
 void
 RememberFsyncRequest(RelFileNode rnode, ForkNumber forknum, BlockNumber segno)
 {
+	/* TEMPORARY INSTRUMENTATION */
+	remember_req_cnt++;
+
 	Assert(pendingOpsTable);
 
 	if (segno == FORGET_RELATION_FSYNC)